Max Power said:
So, if my quick math is correct, the Agfa published time of 16 mins ought to be reduced by about 15% or 144 seconds which gives around 13:30 or so. Aldevo, if I understand you correctly, with a condenser enlarger, this would be somewhere around your recommended time too.
Again, I want to thank everyone who has helped so far, because what I'm looking for is a springboard; a place to start and experiment from.
Cheers!
Kent
Well...I'm not sure where the 15% number comes from exactly. Basically, I've used Rodinal 1:50 w/ APX 100 in some fairly contrasty lighting. When I computed by development time I figured that I'd be conservative (remember, constrasty!) and take a minute off the time published for a gamma of 0.55 - figuring that would be a CI of 0.40 or so. I figured that that CI
might work (and, fortunately,
it did work ) for my 35 mm negs that were to be printed on Forte Polygrade VC with Polymax filters. Given that most of these negs seem to print nicely with a filter grade of 2 1/2 or 3 - I'd say its been successful.
I tend to agree with jdef in that your ability to print at paper grades of 2 or 3 (or filter numbers of the same - though VC filter #s and paper grade #s aren't really the same thing) is a good sign that you've matched development time to your subject contrast and materials.
Just to sum things up regarding all the stuff that flys through my head when I try to nail a development time based on the manufacturer's published time:
What sort of light source do I have on my enlarger? Is it condenser or diffusion? I figure as a rule of thumb a condenser requires about 20-25% less development time than for a diffusion enlarger. How or even whether you adjust your development times from published figures to account for your light source depends upon which type of light source they used to devise the published times. Very often, incredibly, it isn't listed.
Not all condenser light sources are the same, but the differences among them don't seem to upset the apple cart all that much.
How contrasty is my scene? Basically, I use my 35 mm SLR's spotmeter (or wing it if I'm shooting with my Yashicamat 124G for MF) to try to determine the SBR. If the "typical" scene on that roll seemed to include more than 7 stops - I might give it 10% less development time. In extreme cases I'd reduce it more than that but I've yet to encounter any. If its significantly less than 7 stops I might add 10% or even a bit more to the time I devised in the first step.
Of course, the needs of the many outweigh the needs of the few. If I've got a bunch of contrasty subjects and a few flat ones, the constrast ones win out; or, if I'm really certain that the subject in front of me is a keeper I'll change film rolls anyway to avoid having to compromise. Film is (still) cheap.
What's the relationship between my film and paper curves? I'm typically going to try to print on Forte Polygrade V and this paper seems to have a fairly lengthy toe. Rodinal is probably going to give me pretty strong highlight separation so I figure its a wash and won't adjust anything. On the other hand, were I printing on a really short-toed paper like Kodak Polycontrast III (dead and buried) I might drop that development time a little bit. If I were going to use a developer that tended to shoulder off the highlights agressively (and there aren't many that will give me any real shoulder in the useful density range with the films I use) and print those negs on Forte Polygrade (long, sweeping toe = subdued highlight contrast) I might increase the development time a little bit.
In truth, though, I always have two papers in both RC and FB with me in the darkroom. I also make sure I have Agfa Multicontrst papers at hand because these papers seem to have more aggressive highlights separation than the Forte paper and a bit smoother transition to deep shadows. What doesn't work on one usually will do reasonably well on the other. I always start with the assumption that I will print it on Forte Polygrade V.
I suppose I
could add the question of which format am I using to the above. But since I always print on a condenser enlarger, I've found developing to a higher CI for MF vs. 35 mm doesn't really buy me anything. YMMV, of course.
If this sounds serendipitous - you're not wrong. The Zone System it is not, but I do make an effort to keep notes of what works and what does not. In any event, I don't use sheet film or own transmission/reflection densitometers so a "Cumulative Experience Factor Adjustment System" works better for me.